There are many situations in which an interventional cardiologist needs to pass an interventional cardiology device, such as a stent or balloon, beyond a narrowing vascular lesion, or vascular stenosis. Often, it is found that it is possible to pass a guidewire through a stenotic or blocked artery but that the stenosis or blockage prevents the passage of a larger device, such as a balloon or stent carried by an intravascular catheter.
Previous approaches to this problem have often involved attempts to increase the size of the available lumen. This approach generally involves auger-like cardiology devices that seek to drill or abrade their way through a stenotic lesion. This approach is sometimes referred to as debulking the lesion. Examples of such devices are found in U.S. Pat. Nos. 5,078,723, 5,968,064 and 6,666,874. Auger like devices tend to dislodge pieces of atherosclerotic plaques. The dislodged pieces can be released into the blood circulation and create emboli that may create circulatory blockages downstream from the location of the initial stenosis.
Torsional displacement is one of the problems encountered with previous approaches that can happen when applying torque or torsional forces to intravascular catheters. Small diameter intravascular catheters are typically less than two millimeters in diameter and must be flexible to navigate the tortuous paths taken by blood vessels within the body. Materials that allow the desired flexibility tend to not transmit torque forces as well as is desired. That is, the application of torque to a catheter would ideally lead to rotation of the entire catheter about its long axis; however, intravascular catheters made of flexible materials tend to deform under torque loads instead of transmitting the torque force consistently along their length. Depending on the amount of torque applied smoothly at one end of a catheter that torsional force may be transmitted unevenly at the opposing end of the catheter. Thus, a smooth turning at one end may lead to a jerky rotational motion at the other end as torque force is alternately transmitted and stored by torsional displacement of the catheter tube. In a severe case, this may lead to kinking of the tubular portion of the catheter.
It would be desirable to have a catheter that could transmit torque forces evenly along the longitudinal axis of the catheter and with minimal torsional displacement of the catheter while still having enough flexibility to navigate tortuous blood vessels.
It would also be desirable to provide a device that would permit the passage of interventional cardiology devices larger than a guidewire beyond stenotic lesions without dislodging emboli that may create other complications.